Refuses to Crawl

Olivia • 22 years old, single momma 👣 Dominic A. was born April 28, 2016 👶🏼
My son is 6 1/2 months now, and he's still refusing any attempts at crawling. He loves tummy time but won't try pushing himself up, he just flails his arms and legs around when he gets frustrated from not being able to move. He's very advanced everywhere else but just not for crawling. What can I do to help him figure this out?